1. Field of the Invention
This invention relates to a solid electrolytic capacitor and a method of manufacturing the same, and more particularly to a fused chip-type solid electrolytic capacitor and a method of manufacturing the same.
2. Description of the Prior Art
Solid electrolytic capacitors have been widely used in various electronic circuits, which is made advantageous in that a failure rate is small in general. In this case, however, if once the failure is occurred, it often results in a mode of a short circuit. If the short circuit happens, then a large short-circuit current flows to heat the capacitor element and sometimes to burn the capacitor element itself. In order that the capacitor element is prevented from being burnt when the fault due to excessive short-circuit current is happened as well as that other circuit components are protected from being damaged accompanied therewith, it is required that the capacitor element is not to be shorted when a failure is happened. For this, a fuse is generally incorporated into a solid electrolytic capacitor conventionally. Such a solid electrolytic capacitor that a fuse is incorporated as above is called fused solid electrolytic capacitor.
FIG. 1 is a perspective view of a conventional fused chip-type solid electrolytic capacitor, and FIG. 2 is a cross-sectional view of the capacitor shown in FIG. 1. In case of a conventional fused chip-type solid electrolytic capacitor, a capacitor element 1 has an anode lead 2 which is disposed insertedly into the top surface thereof and a cathode layer 3 which is disposed thereon so as to cover the bottom and side surfaces thereof. An anode terminal 4 of a bent metal plate is connected by welding to the anode lead 2 and a cathode terminal 5 of a bent metal plate is adhesively fixed onto the cathode layer 3 with an electrically insulative adhesive material 6. The cathode layer 3 and the cathode terminal 5 are electrically connected to each other through a fuse 7 disposed therebetween in a cross linking manner. Each end of the fuse 7 is connected through a solder 8 to the corresponding one of the cathode layer 3 and the cathode terminal 5. In addition, the fuse 7 itself is entirely covered with an elastic resin 9. The capacitor element 1, anode lead 2, cathode layer 3 and fuse 7 all are encapsulated as an assembly with a rectangular parallelepiped-shaped external resin 10. One end of the anode terminal 4 and one end of the cathode terminal 5 are encapsulated as an assembly with the external resin 10, and the other part of the anode terminal 4 and the other part of the cathode terminal 5 are respectively bent into a L-like shape along the outer-most surface of the external resin 10 thereby to be exposed to the outside thereof.
With the conventional fused chip-type solid electrolytic capacitor as shown above, the following problems have been pointed out to be arisen; first, because the fuse 7 is connected directly to the cathode layer 3 of the capacitor element 1, if an excessive electric current flows to heat the fuse 7, the capacitor element 1 itself may be damaged by burning. In addition, a solder 8 applied onto the cathode layer 3 may be melted by this heat to be thermally expanded, resulting in giving a damage to the external resin 10. Further in addition, the solder to be flowed out from a broken surface of the external resin 10 can make other circuits short electrically, which may result in occurrence of a secondary accident, and in an excessive case, the whole of the circuitry may be catastrophically damaged.
Secondary, the electrically insulative adhesive material 6 is applied in order that the cathode layer 3 of the capacitor element 1 and the cathode terminal 5 are connected to each other while keeping insulation, so that in the process of connecting the fuse 7 thereto, the cathode layer 3 and the cathode terminal 5 may be electrically shorted in the process of curing the electrically insulative adhesive material 6. As a result, it is required to make at least one of the cathode layer 3 and the cathode terminal 5 insulative in advance. In addition, size and shape of the capacitor element 1 are different depending on the capacity and the withstand voltage, so that the position where the fuse 7 and the cathode layer 3 are to be soldered becomes unstable in the process of connecting the fuse 7 thereto, which means that the fuse 7 is difficult to be soldered thereto automatically. For the reasons as shown above, a conventional fused chip-type solid electrolytic capacitor unavoidably becomes sophisticated in the manufacturing process, particularly in the process of connecting a fuse, thus arising such a problem that it is difficult to improve the reliability of fuse connection as well as to reduce the production cost.
This invention was made in consideration of these disadvantages, and an object of this invention is to provide a fused chip-type solid electrolytic capacitor capable of preventing a solder from flowing out from a cathode layer and a capacitor element from being damaged by burning even when a short-circuit is taken place, and a method of manufacturing the same.
Another object of this invention is to provide a fused chip-type solid electrolytic capacitor in which a fuse connection process can be easily automatized, so that the production cost can be reduced while keeping the reliability of fuse connection, and a method of manufacturing the same.